ACHI mode does not really work with the SB600 (some BIOS on certain boards even remove the option). According to that review, the new SB still has issues with AHCI, so I think that's why they did not use it. AMD hyped this SB750 so much that I'm rather disappointed; the "extra overclocking" seems more like a gimmick as well.
No announcement yet.
790GX Vs new 790FX "hawkfish" MB's